Typical iron club heads are solid with a flat hitting face and generally have either a muscle back or a cavity back configuration. Traditionally, all irons had a muscle back configuration, which includes a thicker lower portion, a low offset hosel, a thin top line, a thin sole, and no substantial rear concavity.
Irons with a cavity back configuration have material concentrated toward an outer periphery of the head to form a perimeter weight that defines a rear cavity. The cavity back configuration is used to provide mass distribution that makes the golf clubs more forgiving for less skilled users. For example, the cavity back configuration may be used to locate the center of gravity lower to the ground and rearward to launch a struck golf ball higher. The construction is also generally used to increase the rotational moment of inertia to reduce the golf club's tendency to rotate during imperfect ball strikes thereby providing better directional control.
Additionally, various constructions have been introduced that combine attributes of the muscle back and cavity back constructions. For example, some irons-type club heads include an upper cavity portion and a lower muscle portion. That hybrid construction provides increased forgiveness over a traditional muscle back configuration while providing more efficient energy transfer and improved workability as compared to a pure cavity back construction.
The cavity back and hybrid constructions have been further manipulated to further tune the performance. For example, multi-material constructions have been introduced that incorporate materials having various densities so that the center of gravity can be precisely located. In particular, some golf club heads utilize a body constructed of a medium density material, a face insert constructed of a low density material and sole weight members constructed of a high density material. Additionally, some golf club heads have replaced a portion of the perimeter weight at least partially with a low density material, and oftentimes a portion of the top line is replaced with a low density material to further lower the location of the center of gravity.
Unfortunately, those further manipulations have also altered the vibration and deflection characteristics of the golf club head which contribute to the feel, directional control and energy transfer to the golf ball during impact. Little has been done to structurally tune the golf club body to counteract the deleterious effect of those mass manipulations. Instead, many golf club manufacturers rely solely on a back plate component that is attached to the golf club head and constructed, at least in part, with viscoelastic materials so that they partially dampen undesired vibration.
There remains a need in the art for an improved golf club that includes a structure that tunes the vibration and deflection characteristics of the golf club head.